Update url of testdrive site in README

[mconnew]

It would also be nice if a repo owner could update the url in the repo description.

What this PR does

The previous url in the README redirected to a generic developer site with no mention of edge. This PR fixes the url in the README.

Requirements

• [ ] My PR follows all applicable accessibility requirements (See .github/ACCESSIBILITY_REQS.md). N/A
• [ ] My PR follows the CSS code style guidelines (See .github/CSS_STYLE_REQS.md). N/A
• [ ] I have linted my code using npm run lint:css -- demoDirectoryName/**/*.css and npm run lint:js -- demoDirectoryName/**/*.js, and have fixed the errors. N/A